1. Field of the Invention
This invention relates generally to electronic musical instruments and particularly to a musical tone forming system of the type in which data representative of a musical tone waveform is read out from a waveform storage means to form a required musical tone.
2. Prior Art
There has been proposed one conventional musical tone forming system in which data representing full waveforms of predetermined musical tones is read from an associated waveform storage means to produce musical tone signals. With this conventional system, there can be produced musical tones very close to those produced by a non-electronic or acoustic musical instrument, and particularly this system is suitable for producing percussive tones. This conventional system has been found disadvantageous, however, in that the waveform storage means must have a large capacity for storing the data representative of the full musical tone waveforms. This increases the manufacturing cost of the system.
In order to overcome this disadvantage, another conventional musical tone forming system has been proposed in which an attack or initial portion of each musical tone waveform which has a relatively complicated shape is fully stored in the waveform storage means while part (for example, one cycle) of the other portion of the musical tone waveform is stored in the waveform storage means, the other portion having a less complicated shape. With this arangement, the data representative of the full attack portion is first read out from the storage means and then the data representing the aforesaid part of the other portion is repeatedly read out from the waveform storage means so as to form a musical tone signal representative of a required musical tone. Thus, since the data representative of the aforesaid part is repeatedly used to determine the other portion of the musical tone waveform other than the attack portion, the produced musical tone is inevitably different in nature from that produced by the acoustic musical instrument. Particularly, when a noisy percussive musical tone such as that produced by a cymbal is produced with this conventional system, the resultant musical tone does not accurately exhibit a noisy nature characteristic of such a percussive sound because the same waveform, i.e., the aforesaid part, is successively repeated to provide the other portion of the musical tone waveform following the attack portion.